Preservation of rubber



Patented Sept. 27, 1938 2,131,206 PRESERVATION OF RUBBER Ira Williams, Woodstown, N. J., and Arthur Morrill Neal, Wilmington, Del., assignors to E. I. du Pont de Nemours & Company, Wilmington, Del., a corporation of Delaware No Drawing. Application March 28, 1934, Serial No. 717,796

4 Claims. (Cl. 18-50) This invention relates to the preservation of rubber and more particularly to the treatment of rubber with compounds which retard that deterioration which rubber normally undergoes when exposed to the action of heat, light and oxygen.

It is well known that many compounds possess vide a new class of compounds which are efiective inhibitors of that deterioration which rubber normally undergoes due to the action of light, heat, and oxygen. A further object is to provide a class of compounds which may be added to white or light colored rubber without producing bad discoloration when the rubber containing them is exposed to the action of sunlight. A still further object is to provide rubber compositions having improved properties, particularly unusual resistance to discoloration and deterioration when exposed to the action of light, heat and oxygen. Other objects are to provide new compositions of matter and to advance the art. Still other objects will appear hereinafter.

These objects may be accomplished in accordance with our invention which comprises incorporating in rubber a compound of the type:

in which R represents an ar.-tetra-hydro-naphthyl nucleus and R represents an aryl, aralkyl or alkyl nucleus. When these compounds are incorporated into rubber the resistance of the rubber to deterioration due to the action of light, heat and oxygen is greatly increased. Furthermore, when these compounds are incorporated in light and white colored rubber, such rubber may be exposed to the sunlight for appreciable periods of time without producing bad discoloration. Further, rubber containing these compounds is unusually resistant to that failure usually caused by flexing.

When the term nucleus is employed in this specification and throughout the claims, it will be understood that the group referred to may contain hydroxy, alkoxy, amino and like groups. The term radical as employed in this specification and throughout the claims will be understood to mean that the indicated group is a hydrocarbon group, in other words, consists of carbon and hydrogen, solely. The term "alkyP will be understood to include unsaturated groups such as crotyl, allyi, vinyl, etc., as well as the sat-v urated groups.

Among the compounds which we have found to be particularly satisfactory for our purpose are:

' H H10 N an-tetra-hydro-b-naphthyl-phcnyl amine.

5 v v C Gi i N-N'-dl-ar.-tetra-bydro-bmaplithyl-p-phenylene dlamlne.

of deep nicks and. cracks in the test pieces. The

c H results of this flexing test are given in Table II. E Table II C a Stock Hours a; iailure 5 Hr ar.-tetra-hydro-a-naphthyl-phenyl amine. A 48 2 68 In order to test these compounds the following 5 33 stocks were prepared in which the numbers indi- 10 cate parts by weight. It can be seen from these results that these A B 0 D E Pale crepe 100 100 100 100 100 16 Zinc oxide 100 100 100 100 100 Lithopone 20 20 20 20 20 Stearie acid 1 1 1 1 1 s r a a a a 3 Di'ortho-tolyl-guanidine.. 0.75 0.75 0. 76 0.75 0.76 An-tetra-hydro-b-naphthyl-phenylaminc. 1

Ar.-tetra-hydro-a-naphthyl-phenylamine. 1 20 Ar.-tetra-hydro-b-nsphthyl-p(OH)-phenyl amine 1 N-N-di-ar.-tetrs-hydro-b-nephthyi-pplienylene diamine 1 These stocks were vulcanized. for 45 minutes at compounds are not only eflective in overcoming 25 40 pounds steam pressure. Accelerated aging that deterioration which is due to heat and oxitests were carried out by hanging the vulcanized dation but are also very effective in overcomin slabs in the Bierer Davis bomb in which a conthat failure which is due to flexing. stant temperature of 70 C. and a pressure of 300 The ar.-tetra-hydrc-naphthyl nucleus and the pounds of oxygen were maintained. The results aryl nuclei may contain alkoxy substituents as 80 of this test are given in Table I. in the following compounds.

Table I cm H N O on. Aite 120 h t Stock Original tensile 70 C. an d 8 85 oxygen tensile l p-Methoxy phenyl-ar.-tetrsliydro-b-naphthylamine. A 3,700 Completely deterioratedin48 hours I! 4,115 2,125 on, N- 0C:Hl 4,025 1, 725 40 3,915 2,050 CH: 4,000 2,950 C a As can be seen all of these compounds are ex- 0 1 tremely effective in overcoming that deterioration p-Ethcry-phenyl-an-ietra-hydro-a-napbthylamine.

which is due to heat and oxidation. Further- OH: 45

more, when these white stocks containing ar.- Gem tetra-hydro-b-naphthyl-phenyl-amine or ar.-tetc ra-hydro-a-naphthyl-phenyl-amine are exposed CH:

to sunlight there'is practically no discoloration CHfl 50 produced. Thus it is shown that these deterioram h 1 mm d: hm tion inhibitors are suitable for use in either white p oxymm (my D my an a y 0 mp y mm or light colored stocks. OH H In order to test these compounds further the following stocks were prepared in which the indicated amounts represent parts by weight. on, 00 H 55 b i l CH; A B C D l-phenyi-smino-Mtboxy-ar.-tetta-hydro-naphthalene.

CH: s kd h t 100 100 100 100 H o xid e ii 5 5 5 5 CH N00011:

Carbon black 4o 40 4o 40 Steal-i0 acid. 2 2 2 2 CH,

Suiiur a a a a OCH;

Pine tar 3 3 3 3 CH,

Mercapto-benzo-thiazole 1.25 1. 25 1.25 1.25

Al. tetra hy b p y 2-p-anisyl-arnino3 methoxy-ar.-tetra-hydro-naphthalene.

phenyi- 1.25 65 Aigfietgt iinahbiylgro-a-naphthyl- 1 25 The ar.-tetra-hydro-naphthalene and aryl N-Ndi-ar.-tetra hydro b naph groups may also contain alkyl substituents as in thyl-p-phenylene-dismine 1.25 th f l i o d These stocks were vulcanized for 45 minutes at g on 7 40 pounds and were then tested for their resist- CH: ance to flexing. These tests were made on the I k, machine and by the method described in an article in Rubber Age, Vol. 26, page 542 (1930).

Failure was shown in this test by the appearance 75 H CH: N

o-Tolyl-ar.-tetra-hydro-a-naphthylamine.

. CH: H

2-Phenyl-amino-3-methyl-ar.-tetra-bydro-naphthalene.

p-Ethyl-phenyl-ar.-tetra-hydro-a-naphtbylamine.

2-p-Ethyl-phenyl-amino-a-methyl-ar.-tetra-hydro-naphthalene.

Further, the ar.-tetra-hydro-naphthalene and aryl groups may contain substituted amino substituents as in H: p-Morpholyl-phenyl-ar tetra-hydro-b-napbthylaminel onron,

p-Dimethyl-amino-pl1enyl-ar.-tetra-hydro-b-nuphthylamine.

Compounds in which R represents aralkyl and alkyl substituents may be represented by the following on, cl,

H N-C H1 Benzyl-ar.-tetra-bydro-b-naphthylamlne.

Ethyl-m'.-tetra-hydrob-naphthylamine.

} vulcanization by means of any of the well known 75 9H2 H H2? N-CaHl 1120 H: Propyl-aL-tetra-hydro-b-naphthylamine.

2 Methyl-er.-tetm-hydro-a-naphthylamine.

15 H CH2 N.CnHs

Ethyl-arl-tetra-bydro-a-naphthylnmine.

. OCH: E H 25 CH: N-0H CH2 I Meta-methoxyl-benzyl-ar.-tetra-liydro-Bmaphthylamine. 30

on, H CIH NCHa-CH20H CH2\ I 4 CH2 35 B-(OH)-ethyl-ar.-tetra-hydro-B-naphthylamine. Compounds in which R represents other aryl nuclei than phenyl may be illustrated by the fol o lowing compounds H or l, CH1

Xenyl-ar.-tetra-hydro-B-naphthyla1nine.

B-naphthyl-ar.-tetra-bydro-B-nnphthylamine.

CHI H 0 N Ci ia ll-anthryl-ar.-tetm-hydro-B-naphthylmnine.

The compounds disclosed in the examples and those mentioned above are merely illustrative of the compounds of our class. It will be understood 5 that the various homologues and analogues of the compounds specifically disclosed may also be employed. Also, when R represents aralkyl and alkyl nuclei such nuclei may contain amino, hydroxy and alkoxy groups.

Our compounds will generally be incorporated in rubber by milling them into the 'rubber prior to vulcanization. However, they can be incorporated into the rubber either before or after methods 01' impregnation. Also, the amounts added may be varied within an extremely wide range depending upon the composition 0! the rubber stock and the desire of the user.

While we have disclosed the preferred embodiments of our invention, it will be readily apparent to those skilled in the art that many variations and modifications may be made therein without departing from the spirit thereof. Accordingly, the scope of our invention is to be limited solely by the appended claims construed as broadly as is permissible in view of the prior art.

We claim:

1. The method of preserving rubber which comprises incorporating therein a secondary N-aromatic ar.-tetra-hydro-naphthylamine in which the aromatic group contains a substituent selected from the group of hydroxy, alkoxy and amino groups said aromatic group being otherwise free of substituents other than hydrocarbon substituents.

2. The method of preserving rubber which comprises incorporating therein a secondary N-aromatic ar.-tetra-hydro-naphthylamine in which the aromatic group is or the benzene series and contains a substituent selected from the group of hydroxy, alkoxy and amino groups said aromatic group being otherwise free of substituents other than hydrocarbon substituents.

3. Rubber having incorporated therein a secondary N-aromatic ar.-tetra-hydro-naphthylamine in which the aromatic group contains a substituent selected from the group of hydroxy, 

